What "expressive monosyllable" is Oliver referring to, then?
"'Then I'll whop yer when I get in,' said the voice; 'you just see if I don't, that's all, my work'us brat!' and having made this obliging promise, the voice began to whistle.
Oliver had been too often subjected to the process to which the very expressive monosyllable just recorded bears reference, to entertain the smallest doubt that the owner of the voice, whoever he might be, would redeem his pledge, most honourably."